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United States Patent |
5,672,444
|
Kuriyaki
,   et al.
|
September 30, 1997
|
Composite electrode for a photo-rechargeable storage battery
Abstract
A composite electrode for a photo-rechargeable storage battery includes a
filter paper of glass fiber as a base material; a polypyrrole film coated
on a surface of the filter paper to provide a conductive polymer; and a
gel of polytungustic acid provided on the polypyrrole film in the form of
a cluster to provide a photo-catalytic property. The polypyrrole film may
be vapor phase polymerized and coated onto a surface of the filter paper
and the gel of polytungustic acid may be vapor phase coated onto the
polypyrrole film in the form of a cluster. Thus, all electrode
manufacturing steps can be carried out in the vapor phase so that
manufacturing of such an electrode having a very large specific surface
area is practical and large electrode areas may be manufactured.
Inventors:
|
Kuriyaki; Hisao (Fukuoka, JP);
Hirakawa; Kazuyoshi (Fukuoka, JP);
Nomiyama; Teruaki (Kagoshima, JP)
|
Assignee:
|
Kyushu University (Fukuoka Pref., JP)
|
Appl. No.:
|
621031 |
Filed:
|
March 22, 1996 |
Foreign Application Priority Data
Current U.S. Class: |
429/213; 257/E51.012; 257/E51.028; 429/111 |
Intern'l Class: |
H01M 006/30; H01M 004/60 |
Field of Search: |
429/111,213
|
References Cited
U.S. Patent Documents
4338180 | Jul., 1982 | Hanamura | 429/111.
|
Primary Examiner: Maples; John S.
Attorney, Agent or Firm: Spencer & Frank
Claims
What is claimed is:
1. A composite electrode for a photo-rechargeable storage battery,
comprising:
a filter paper of glass fiber as a base material;
a polypyrrole film coated on a surface of the filter paper; and
a gel of polytungustic acid provided on the polypyrrole film in the form of
a cluster.
2. A composite electrode for a photo-rechargeable storage battery,
comprising:
a filter paper of glass fiber as a base material;
a polypyrrole film vapor phase polymerized and coated onto a surface of the
filter paper; and
a gel of polytungustic acid vapor phase coated onto the polypyrrole film in
the form of a cluster.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photo-rechargeable storage battery
having an electron storage property with light different from a solar
cell, particularly capable of large areas and having high efficiency, and
particularly to a manufacture of a new semiconductor electrode having an
extremely large ratio of surface area and a large photo reactive site.
Also, the present invention relates to an electrode material for optical
energy conversion used for a photo rechargeable storage battery, a solar
cell or the like.
A photo rechargeable storage battery is a device capable of performing
optical energy conversion and recharging with a unit electrode.
2. Related Art Statement
Hitherto, a photo rechargeable storage battery was investigated employing
one substance having both semiconductivity and an electron storing
property, but in this case, the energy conversion efficiency and the
electron storing efficiency are low, respectively, and its practical
utilization is still a long way off. As an electrode material, a layer
compound semiconductor (intercalation compound semiconductor) and a
macromolecular material having semiconductivity were studied. In this
case, however, in addition to the above various low efficiencies,
manufacturing steps become complicated, and it is difficult to put this
material to practical use as a solar light device requiring large area.
Therefore, it is necessary to develop an electrode having sufficient
energy conversion and storing efficiencies, and to obtain a method of
easily manufacturing the electrode having large area with simple
fabricating steps.
That is, the material capable of putting it to practical use is not found,
since the dissolution of the electrode or the like arises in the
intercalation compound. Moreover, in the usual silicon solar cell, it is
possible to make an area of vapor deposition film large, but in the
intercalation compound having photo rechargeable property, such a
manufacturing method is not established, so that this becomes a large
stretch to put in to practical use.
Moreover, a macromolecular material (polythiophene or the like) having a
semiconductive property is also known as a electrode material for photo
rechargeable storage battery, but for the photo rechargeable property,
enough efficiency to obtain it, as in the intercalation compound, can not
be obtained. In this way, an electrode material of practical utility for a
photo rechargeable storage battery has been not yet reported.
Therefore, it is necessary to manufacture an electrode having sufficient
energy conversion efficiency and storage efficiency. Photo-recharging
consists of two reactions, that is, a reaction of separating photo
excitation carriers in a semiconductor and a reaction of recharging the
carriers. A conventional electrode material is a material having both a
semiconductor property and charging capability, so that it is difficult to
find or synthesize a material having suitable characteristic from the
viewpoint of both of the above considerations.
SUMMARY OF THE INVENTION
The present invention is based on the fact that processes of light-energy
conversion and charging are performed respectively by utilizing different
materials, and these materials are composed to form a composite electrode,
and then, this composition is performed with few micron unit by noting
microscopic property of the electrode, thereby obtaining realization of
photo-rechargeable property with high efficiency.
Moreover, in order to put it to practical use, it is also necessary to
manufacture the electrode having large area with simple manner. To this
end, a conductive polymer as a charging electrode and a semiconductor
performing light-energy conversion are polymerized with a filter paper as
a base material in vapor phase, thereby forming a composite electrode
capable of utilizing respective fibers of the filter paper as an
electrode.
It is an object of the present invention to eliminate the above described
disadvantages of the conventional photo-rechargeable storage battery.
It is another object of the present invention to provide a high performance
photo-rechargeable storage battery capable of making an area of the
battery large, and a method of manufacturing the same.
It is other object of the present invention to provide a method of
manufacturing a semiconductor electrode having very large specific surface
area by leading a polymerization of a filter paper as a base material in
vapor phase, and by manufacturing an electrode on fiber of the filter
paper and fixing a semiconductor material on the electrode in the form of
fine particle, in the manufacturing process of a solar light energy
device, and thus to provide a practical storage battery capable of
charging with light.
According to the present invention, there is provided a photo-rechargeable
storage battery comprising a composite electrode, said electrode being
manufactured by vapor phase-polymerizing a polypyrrole and a gel of
polytungustic acid on a filter paper, this composite electrode being
utilized as an electrode of the storage battery.
According to the present invention, in order to manufacture the
photo-rechargeable storage battery capable of being charged with light, on
the assumption that the manufacturing method is simple and expensive
material is not utilized, the composite electrode is manufactured by
making a conductive polymer as a base. As a method of making efficiency
high, in order to manufacture an electrode having large specific surface
area per unit area, the technique of coating conductive polymer on the
surface of the fiber of filter paper and the technique of adhering
material having photo-catalytic property on the conductive polymer film in
the form of a cluster are developed, thereby manufacturing a high
performance photo-rechargeable storage battery, finally.
In an embodiment of the photo-rechargeable storage battery according to the
present invention, there is provided a photo-rechargeable storage battery
comprising a composite electrode, said electrode comprising a filter paper
of glass fiber as a base material, a polypyrrole film coated on a surface
of the filter paper, and an electrode formed by carrying a gel of
poly-tungustic acid on the glass fiber coated with the polypyrrole film in
the form of cluster shape.
According to the present invention, there is provided a method of
manufacturing a photo-rechargeable storage battery comprising a composite
electrode, the manufacture of said composite electrode comprising steps
of:
preparing a filter paper of a glass fiber as a base material,
immersing a sodium tungstate into the filter paper, and,
introducing a hydrochloric acid as a catalytic vapor into the immersed
filter paper in a gas phase, thereby forming a fine electrode with the
utilization of chemical polymerization at the fiber surface, and
repeating these steps, thereby forming an electrode having an extremely
large ratio of surface area capable of adding different functions with the
use of a vapor phase polymerization.
In a further preferable embodiment of the method according to the present
invention, there is provided a method of manufacturing a
photo-rechargeable storage battery comprising a composite electrode, the
manufacture of said composite electrode comprising steps of:
cutting a filter paper of glass fiber as a base material in an optional
form,
washing the cut filter paper,
coating a polypyrrole film on the surface of the filter paper, and
carrying a gel of poly-tungustic acid on the glass fiber of the coated the
polypyrrole film on the surface of the filter paper in the form of cluster
shape, thereby forming an electrode.
In the other method of manufacturing a photo-rechargeable storage battery
according to the present invention, the method comprises a composite
electrode, the manufacture of said electrode comprising a step of
producing a polypyrrole electrode, and a step of carrying photo-catalyst
on the polypyrrole electrode, the polypyrrole electrode producing step
comprising steps of:
cutting a filter paper of glass fiber as a base material in an optional
form,
washing the cut filter paper,
immersing the washed filter paper in solution of oxidizing,
masking the required portion of the filter paper,
inserting the masked filter paper in a desiccator and reducing pressure in
the desiccator,
leading pyrrole gas in the desiccator,
leaving it for required hours,
taking out the filter paper from the desiccator,
washing unreacted group, and
the photo-catalyst carrying step comprising steps of:
immersing the thus treated filter paper in solution of sodium tungstate,
masking the required portion of the immersed filter paper,
inserting the masked filter paper in the desiccator and reducing pressure
in the desiccator,
leading hydrochloric acid vapor as a reaction gas in the desiccator,
leaving it for required hours,
taking out the filter paper from the desiccator, and
washing unreacted group, thereby forming a composite electrode on the
filter paper by a vapor phase polymerization method.
According to the present invention, as described above, a glass fiber
filter paper is used as a base material, oxidation catalyst is previously
immersed in the filter paper, the immersed filter paper is inserted in the
desiccator, pressure is reduced, and then, the conductive polymeric
monomer capable of being charged is lead in the desiccator. This process
makes the conductive polymer polymerized, thereby coating respective
fibers of the filter paper with rechargeable polymer film. As in the same
manner, the thus coated filter paper is immersed in a solution of
polytungustic acid, and is treated with hydrochloric acid vapor, so that
gel of oxidized tungustic acid becomes particle shape of order of few
.mu.m, and fixed on the fiber coated with polymer. Therefore, the
respective fibers of the filter paper become a photo-electrode which is
formed of fixed gel of tungustic acid having semiconductor property, so
that the electrode having very large specific surface area and the
photo-reaction site can be manufactured.
In the present invention, respective fibers of the filter paper are coated
with polymer causing rechargeable reaction by polymerizing vaporized
polymeric monomer with glass fiber filter paper immersed in solution of
oxidizing agent. Moreover, the gel of polytungustic acid having particle
diameter of few .mu.m and exhibiting semiconductor property is fixed. This
manufacturing process may be realized with the same fabricating apparatus
and the same steps, so that this manufacturing method is very simple and
the electrode with very large area can easily be made by using inexpensive
filter paper as a base material and by manufacturing the electrode in
vapor phase.
Moreover, in the electrode made by using inexpensive filter paper as a base
material and by manufacturing it in vapor phase, respective fibers become
an electrode, so that the electrode has very large specific surface area
for apparent area and thus the current density per unit area may be
improved largely. Also, polytungustic acid having semiconductor property
can be fixed in the form of particle having particle diameter of few
.mu.m, so that light-energy conversion can be realized with high
efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1(A), 1(B) and 1(C) are a step summary view showing manufacturing
procedure of a composite electrode using a filter paper in a vapor phase,
an explanatory view of treating the filter paper in a solution, and a
diagram of a vapor reaction treating apparatus in a desiccator according
to the present invention;
FIG. 2(A) is a microstructure view showing a surface state (condition) of
fiber of the filter paper before treating with a scanning electron
microscope observation;
FIG. 2(B) is a microstructure view of the fiber after polypyrrole coating
treatment showing a state of adhering the polypyrrole conductive film on
the surface without destroying the structure of the filter paper;
FIG. 2(C) is a microstructure view of fiber of the filter paper electrode
after a treatment of gel of polytungustic acid showing that the gel is
diffused and fixed with the particle diameter of few .mu.m;
FIG. 3 is a characteristic view showing a relationship between a
discharging current and a lapse of time in the cases of first light
irradiation on the composite electrode according to the present invention,
of non-light irradiation, and of second light irradiation, respectively;
FIG. 4 is a characteristic view showing a relationship between a
discharging current and a lapse of time in case of coating only
polypyrrole on the filter paper;
FIG. 5 is a characteristic view showing photocharging currents charged by
light, which is obtained by reducing the discharged currents in case of
performing non-light irradiation from the discharge current after second
light irradiation;
FIG. 6 is a characteristic view of photocharging currents obtained by
subjecting a comparative examination of an electrode obtained by forming a
conductive film having rechargeability of polypyrrole on the filter paper
and forming sol of polytungustic acid (PTA) on the thus formed conductive
film and CuFeTe.sub.2 of the intercalation layer semiconductor compound;
and
FIG. 7 is a characteristic view obtained by comparing a cyclic voltamograph
in case of carrying TiO.sub.2 of different photo-catalyst and sol of
polytungustic acid on the electrode of polypyrrole filter paper according
to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the drawings, there is shown an embodiment of a photo-rechargeable
storage battery according to the present invention. As an embodiment, a
method of manufacturing an electrode in a vapor phase with the use of a
filter paper is explained with reference to FIG. 1 where valves 5 control
gas flows. In this embodiment, polypyrrole is selected as a rechargeable
material, and a gel of polytungustic acid is selected as a light-energy
conversion material. The method of manufacturing an electrode in a vapor
phase with the use of a filter paper is concretely shown in FIG. 1. At
first, a glass fiber filter paper 1 is cut out in an optional form, and is
washed with a distilled water. In this example, the filter paper is cut
out in 1.times.4 cm.sup.2 and immersed in a solution 2 of oxidizing agent
(solution of FeCl.sub.3) so as to form a polypyrrole film on the surface
of the filter paper. Then, the filter paper thus treated is masked at a
required site, inserted in a desiccator 3, and subjected to a reduced
pressure treatment by a vacuum pump for few minute. Then, pyrrole vapor
generated from pyrrole in liquid phase 4 which is held in the reduced
pressure desiccator to the extent of 70.degree. C., is lead to commence
performing an oxidative polymerization on the filter paper, and left for a
few hours as it is, thereby forming a black polypyrrole film on the
surface of the filter paper. After sufficient polymerization, excess
unreacted substance is washed away with distilled water, thereby forming
an electrode of polypyrrole treated filter paper.
In this case, polypyrrole is uniformly adhered onto the surface of
respective fibers of the filter paper, without preventing porosity of the
filer paper itself. In this way, polypyrrole treated filter paper becomes
an electrical conductor having resistivity of substantially 10.sup.3 to
10.sup.4 ohm/cm.sup.3 in the surface direction of the filter paper
(1.times.1 cm.sup.2).
Then, gel of polytungustic acid is carried and fixed on the polypyrrole
film. This fixation may be performed in the vapor phase in the same manner
as in the formation of polypyrrole. In this case, a solution 2 of sodium
tungustic acid is used instead of the solution 2 of oxidizing agent and
hydrochloric acid is used instead of polypyrrole. The gel of polytungustic
acid formed on the filter paper is fixed on the fiber of the filter paper
in the form of fine particles in the same procedure. A schematic diagram
in which the electrode of filter paper is observed by a scanning electron
microscope, is shown in FIG. 2. The magnitude of the fine particle can be
controlled by changing the concentration of the solution of sodium
tungustic acid.
Since whole manufacturing steps are proceeded in the vapor phase, the
regions carrying the reaction substance are masked as described above, so
that this embodiment has a merit that the treating steps can simply be
controlled.
FIG. 2 shows the construction of the composite electrode thus manufactured.
In FIG. 2(A), reference numeral 6 is a fiber of the glass fiber filter
paper, reference numeral 7 is a fiber of the filter paper after
polypyrrole coating, and reference numeral 3 is a fine particle of gel of
tungustic acid.
This electrode is manufactured in such a manner that the polypyrrole
electrode portion and the carrying portion of gel of polytungustic acid
form an interface. Also, schematic diagrams in which the electrode surface
of filter paper is observed by the scanning electron microscope, are shown
in FIGS. 2(A), 2(B) and 2(C), respectively.
FIG. 3 shows a graph of discharging property obtained by examining a
performance of a photo-rechargeable storage battery with the use of this
electrode. This graph shows a comparison of a discharging current obtained
by performing discharge for a reference electrode (Ag/AgCl electrode)
after light irradiation for ten minutes with a discharging current
obtained in case of performing non-light irradiation with the same
procedure. In FIG. 3, abscissa shows a discharging time (minutes). In this
measuring, aqueous solution of perchloric acid (1 mol/l) is used as an
electrolyte, and xenon light (strength of irradiating light on electrode
surface: 3 W/cm.sup.2) having spectral near solar light is used as a light
source. As seen from this graph, the discharging current after light
irradiation is larger than that in the case of non-light irradiation, so
that this shows the feature of having the photo-rechargeable storage
property. The photocharging currents charged by light, which is obtained
by reducing the discharged currents in case of performing non-light
irradiation from the discharge current after light irradiation, is shown
in FIG. 5. The magnitude of the photo-charging currents charged by light
is an order of few hundreds .mu.A, which is a sufficiently practical value
in case of considering a light irradiation for ten minutes. The method of
manufacturing electrode utilizing the filter paper in the vapor phase may
also be applied to another conductive polymer. TiO.sub.2 which has a many
utilizations as a photo-catalyst, may also be carried in the fine cluster
shape in the same way as the above, so that the present invention is
technics having a wide application range, in addition of application to
the photo-rechargeable storage battery.
FIG. 3 shows a characteristic view showing data of photo-charging currents
(FIG. 5) of the composite electrode according to the present invention.
The characteristic diagram showing photo-charging currents shown in FIG. 5
is obtained by exhibiting the difference between the discharging current
in the case of non-light irradiation and the discharging current after the
second light irradiation as a photo-charging current. While the measuring
result shown in FIG. 5 exhibits the data obtained in case of repeating a
following cycle continuously:
light irradiation for ten minutes.fwdarw.discharging (discharging after
first light irradiation).fwdarw.non-light irradiation.fwdarw.discharging
(discharging after non-light irradiation).fwdarw.light irradiation for ten
minutes.fwdarw.discharging (discharging after second light irradiation)
The curves of photo-charging currents shown in FIG. 5 demonstrate that the
recharging by the light is realized, since the discharging current after
the second light irradiation is larger than the discharging current with
non light irradiation (dark discharging).
FIG. 4 shows a characteristic diagram of the discharging current of the
electrode which is formed by coating and polymerizing only polypyrrole on
the filter paper, in order to exhibit that photo-rechargeability is caused
only by manufacturing composite electrode.
By performing the same measurement as that shown in FIG. 3, it is found
that in the electrode having only polypyrrole provided thereon, the
discharging current is decreased with time lapse, irrespective of presence
of light, so that electrode without gel of polytungustic acid does not
have the photo-rechargeability.
FIG. 5 is a characteristic diagram of a photo-recharging current of the
composite electrode according to the present invention, and this current
is obtained as the difference between the discharging current with non
light irradiation and the discharging current after second light
irradiation.
The comparison between the composite electrode according to the present
invention and the other electrode is shown in following table 1.
Table 1 shows the relationship among the composition of following
electrodes, the magnitude of the photo-recharging current
(photo-rechargeability), and the photo-voltaic force.
TABLE 1
______________________________________
Comparison to other electrodes
______________________________________
##STR1##
______________________________________
(1) CuFeTe.sub.2
(2) Gel of polytungustic acid+graphite (film electrode)
(3) Polythiophene
(4) Polypyrrole
(5) Composite electrode according to the present invention
The data shown in the table 1 should be compared with data of other
research worker, but the research that the discharging current after light
irradiation is measured as in the present invention, is not found, so that
only the data measured by present inventors are illustrated.
It is found from this table 1, that the photo-recharging current of the
composite electrode according to the present invention is very large.
FIG. 6 shows a comparison of characteristics of the photo-recharging
current charged by light with the use of both CuFeTe.sub.2 having
comparative large photo-rechargeability and the composite electrode
according to the present invention. It is found from FIG. 6 that the
composite electrode according to the present invention flows the
photo-recharging current having the order of tens times of that of
conventional electrode, and thus this composite electrode has a high
photo-rechargeability.
Experimental example
The present inventors have tested the photo-rechargeability of series
obtained by dispersing photo-functional particles into conductive polymer
having recharging property. In conventional electrode, polythiophene is
used as a conductive polymer. However, polythiophene has semiconductivity
in the condition that doping is not performed, so that it is difficult to
design an electrode so as to respond it to light together with the
photo-functional particles. However, in the present invention, polypyrrole
which has comparatively metallic conductivity is used as a conductive
polymer, and its electro-chemical property and photo-rechargeable property
are tested. Polypyrrole is apt to polymerize as compared with
polythiophene, so that various manufacturing method are possible and thus
the manufacture of composite electrode can be realized by combining it
with the photo-functional particles.
Manufacture of electrode
A filter paper which is applied by solution of FeCl.sub.3 is treated with
pyrrole vapor, thereby forming a polypyrrole electrode. In this way,
polypyrrole electrode can be manufactured having flexibility and strength
by using the filter paper as basic material. TiO.sub.2 as a
photo-functional particle and sol of polytungustic acid are carried onto
the polypyrrole electrode, thereby forming a composite electrode.
Result
FIG. 7 shows a cyclic voltammogram graph of the polypyrrole filter paper
electrode obtained by dispersing TiO.sub.2 powder and sol of polytungustic
acid and carrying them onto the filter paper. It is found from FIG. 7 that
when TiO.sub.2 powder of various amount of photo-functional particles and
various amount of sol of polytungustic acid are carried onto the
polypyrrole filter paper respectively, various cyclic voltammogram graphs
may be obtained. This means that charge migration between the polypyrrole
filter paper electrode and the photo-functional particles is present.
Moreover, it is found that the polypyrrole electrode using this filter
paper increases its reacting region by reflecting porous of the filter
paper, and large current can be obtained as compared with conventional
film electrode due to common electro-deposition.
As described above, according to the present invention, high performance
electrode having very high ratio surface area can be manufactured by
applying a manufacture of electrode in the vapor phase with the use of the
filter paper as a base material to other devices. Moreover, the
semiconductor can be fixed as a particle, so that the present invention
can be applied to other devices utilizing a size effect which is not
present in the conventional semiconductor electrode. This manufacturing
technic is very general purpose technic, since it can be applied to other
semiconductor material capable of manufacturing it with the sol-gel method
and other polymer.
Moreover, various different kinds of semiconductor materials may be mixed
as a fine particle, so that a photo-electrode having wide absorption
spectrum can be manufactured by forming composite electrode with the use
of semiconductor having different light absorption bands. In this way, the
manufacture of electrode in the vapor phase with the use of the filter
paper as a base material is very advantageous in industry.
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